1. Field of the Invention
The invention relates to apparatus for use in measuring the slope of pipelines and more particularly to apparatus employing a fluid filled conduit having pressure sensing transducers attached to its opposite ends. One end of the fluid filled conduit, having a pressure sensing transducer attached thereto, is adapted to be pulled through the pipeline. Means are also provided to compare the output signals of the pressure sensing transducers to yield an elevation differential output.
2. Description of the Prior Art
Attention is directed to the Moore U.S. Pat. No. 2,709,920, issued June 7, 1955 and illustrating apparatus for determination of the elevation of a pipeline and including a flexible fluid conduit which is to be pulled through a pipeline and including a relief valve attached to that end of the conduit intended to be pulled through the pipeline. A pressure gauge is attached to the opposite end of the conduit. In operation, as the pressure relief valve is pulled through the pipeline, fluid in the conduit is exhausted through the relief valve and the pressure in that end of the conduit remains approximately constant. Determination of the difference between the pressure indicated by the pressure gauge and the known pressure at the pressure relief valve will yield the height difference between the pressure gauge and the end of the conduit conveyed through the pipeline. The structure shown in the Moore patent has the disadvantage that fluid must be continuously supplied to the fluid filled conduit and the mechanical pressure relief valve is not sufficiently sensitive to accurately indicate the slope of a pipeline.
Attention is also directed to the Gearhart U.S. Pat. No. ,3,815,424, issued June 11, 1974; the Rosa et al. U.S. Pat. No. 3,835,707, issued Sept. 17, 1974; the Bowditch et al. U.S. Pat. No. 4,026,156, issued May 31, 1977; and the Meents et al. U.S. Pat. No. 2,851,799, issued Sept. 16, 1958. Attention is also directed to the Nilsson U.S. Pat. No. 3,779,084, issued Dec. 18, 1973; and the Harland U.S. Pat. No. 3,724,278, issued Apr. 3, 1973.